The present invention concerns the formation of compositionally and morphologically uniform metal alloys and catalysts at low temperature.
Metal alloys, such as copper-nickel (Cu-Ni), are well established as catalysts for a number of chemical processes. In hydrogenation reactions, alloy composition is known to affect significantly both catalyst activity and selectivity.
Gu-Ni catalysts can be prepared by a number of standard metallurgical and powder metallurgical techniques. Alloy formation in the Cu-Ni system is an endothermic process and alloys tend to exhibit compositional inhomogeneities in the form of local regions of relatively pure copper and pure nickel. A long careful annealing treatment is generally required to reach equilibrium and obtain single-phase homogeneous alloys. Techniques which tend to minimize inhomogeneities with a minimum of processing are therefore of great interest.
In any catalyst a high surface area is generally desirable and usually leads to high catalyst activity. Low temperature decomposition of inorganic or organometallic precursors is a potential route to high surface area alloys. Because of the endothermic nature of the Cu-Ni system, formation of single-phase homogeneous alloys may present a problem.
In a study of Cu-Ni alloy formation via the hydrogen reduction of metal carbonate precursors it was reported that fairly homogeneous alloys were obtained, but it was not clear that these were completely single phase. As a further consideration, the reported critical temperature for single-phase Cu-Ni alloy formation is 320.degree. C. Thus, the decomposition temperature of the precursors would be expected to affect the homogeneity and extent of single-phase alloy formation.
It is therefore the principal object of the present invention to provide a method for forming single-phase metal alloys of high surface area at low temperatures.